The people are making great efforts to develop the preparation of a unique material, i.e. organic/inorganic nanocomposite microspheres, and in particular, the magnetic composite microsphere is drawing the attentions of developers for its potential applications in biology. The methods generally used to prepare the inorganic/organic composite nano-microspheres include: suspension polymerization, dispersion polymerization, emulsion polymerization, miniemulsion polymerization and the like. The suspension polymerization and dispersion polymerization can produce composite microspheres particles with larger particle size but also relatively wider particle size distribution; as to the typical emulsion polymerization, the composition degree of the particles tends to degrade and the contents of the inorganic dispersed phase will be inhomogeneous due to the limitation in the polymerization mechanism thereof; miniemulsion polymerization is a preferable process for preparing inorganic/organic composite microspheres, however, the miniemulsification process can not achieve a substantial mono-dispersed miniemulsion, therefore the microspheres thus prepared are of uneven particle size distribution, and it's hard to increase the amount of inorganic particles in the microspheres.
After searching the literatures of the prior art, we find that the magnetic particles content in the magnetic polymer nanocomposite microspheres prepared by conventional methods such as dispersion polymerization, emulsion polymerization, suspension polymerization, etc. is not more than 35 wt %. A three-step process for preparing composite microsphere with high magnetic particles content is disclosed in “Magnetic Polystyrene Nanoparticles with a High Magnetite Content Obtained by Miniemulsion Processes”, Macromolecular Chemistry and Physics 2003. 204. 22-31, developed by Lilliana P. Ramirez and Katharina Landfester, etc., thereby the magnetic particles content in magnetic polystyrene is increased to 40 wt %. However, the magnetic polystyrene microspheres produced by this three-step miniemulsion polymerization have wide particle size distribution and do not exhibit excellent morphology.